Software defined automotive radar systems

ABSTRACT

A radar system processes signals in a flexible, adaptive manner to determine range, Doppler (velocity) and angle of objects in an environment. The radar system processes the received signal to achieve different objectives depending on the environment, the current information stored in the radar system, and/or external information provided to the radar system. The system allows improved resolution of range, Doppler and/or angle depending on the desired objective.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the filing benefits of U.S. provisionalapplications, Ser. No. 62/327,003, filed Apr. 25, 2016, Ser. No.62/327,004, filed Apr. 25, 2016, Ser. No. 62/327,005, filed Apr. 25,2016, Ser. No. 62/327,006, filed Apr. 25, 2016, Ser. No. 62/327,015,filed Apr. 25, 2016, Ser. No. 62/327,016, filed Apr. 25, 2016,62/327,017, filed Apr. 25, 2016, and Ser. No. 62/327,018, filed Apr. 25,2016; and is a continuation-in-part of U.S. patent application Ser. No.15/481,648, filed Apr. 7, 2017, which claims the filing benefits of U.S.provisional applications, Ser. No. 62/319,613, filed Apr. 7, 2016, andSer. No. 62/327,003, filed Apr. 25, 2016, which are all herebyincorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The present invention is directed to radar systems, and in particular toradar systems for vehicles.

BACKGROUND OF THE INVENTION

The use of radar to determine range, velocity, and angle (elevation orazimuth) of objects in an environment is important in a number ofapplications including automotive radar and gesture detection. A radartypically transmits a radio frequency (RF) signal and listens for thereflection of the radio signal from objects in the environment. A radarsystem estimates the location and velocity of objects, also calledtargets, in the environment by comparing the received radio signal withthe transmitted radio signal. It would be advantageous to have a radarsystem that can adapt various aspects of the radar transmitted signaland receiver processing to different environments and differentobjective functions.

SUMMARY OF THE INVENTION

The present invention provides methods and a radar system that canoperate under a variety of environments, a variety of externalinformation, and with a variety of objective functions to modify thetransmission and reception processing at a given time to optimize thesystem with respect to a given objective function. The inventionaccomplishes better performance by adaptively changing the systemincluding changing the transmitted signal characteristics such as thebaseband signal, the bandwidth, the frequency, and the power and the setof transmitting antennas that are used. Better performance is alsoobtained by changing the receiver processing including the receivingantennas, interference mitigation techniques to be employed, length oftime of the signal used to process a received signal to determine range.

A radar sensing system for a vehicle in accordance with an embodiment ofthe present invention includes a plurality of transmitters, a pluralityof receivers, a memory, and a control unit. The plurality oftransmitters is configured for installation and use on a vehicle andoperable to or configured to transmit modulated radio signals. Theplurality of receivers are configured for installation and use on thevehicle and operable to or configured to receive radio signals that aretransmitted radio signals reflected from an object in the environment.Each transmitter of the plurality of transmitters comprises a digitalprocessing unit, a digital-to-analog converter, an analog processingunit, and a transmit antenna. Each receiver of the plurality ofreceivers comprises a receive antenna, an analog processing unit, ananalog-to-digital converter, a digital front end processing unit, and adigital back end processing system. The control unit is operable to orconfigured to select an operating mode and to modify the plurality oftransmitters and the plurality of receivers. Range information dataproduced by the digital front end processing unit is stored in thememory and then processed by the digital back end processor, as directedby the control unit. The range information data, which includes rangeinformation of objects in the environment, is stored in the memory fordifferent receivers and for different scans. The processing of the rangeinformation data is controlled by the control unit.

A method for operating a dynamically adaptable, modulated continuouswave vehicular radar system in accordance with an embodiment of thepresent invention. The method includes providing a transmitter and areceiver, both configured for installation and use on a vehicle. Thetransmitter is operable to or configured to transmit a modulated radiosignal. The receiver is operable to or configured to receive a radiosignal that is a transmitted radio signal reflected from an object inthe environment. The receiver comprises a dynamically adaptable digitalfront end processor and a dynamically adaptable digital back endprocessor. In response to environmental conditions and an operationalstatus, an operating mode and a modification of an operational parameterof at least one of the transmitter and the receiver are selected, theselection depending on a need for one of a best range resolution and abest velocity resolution. Range information data is stored into memorythat was produced by the digital front end processing unit. The digitalback end processor is directed to process a selected portion of therange information data, based upon the selected operating mode.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an automobile equipped with a radar system inaccordance with the present invention;

FIGS. 2A and 2B are block diagrams of single transmitter and receiver ina radar system;

FIG. 3 is a block diagram of multiple transmitters and multiplereceivers in a radar system;

FIG. 4 is a block of a single receiver and single transmitter;

FIG. 5 is a graph illustrating an exemplary transmitted signal using anm-sequence of length 31 in accordance with the present invention;

FIGS. 6-9 are graphs illustrating exemplary matched filter outputs overtime in accordance with the present invention;

FIG. 10 is a graph illustrating an exemplary imagery part of filteroutput vs a real part of filter output in accordance with the presentinvention; and

FIGS. 11a, 11b, 11c, and 11d are block diagrams illustrating exemplarysteps to signal processing in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to theaccompanying figures, wherein numbered elements in the following writtendescription correspond to like-numbered elements in the figures. Methodsand systems of the present invention may achieve better performance froma radar system when there is a near object and a far object. Exemplaryembodiments of the present invention accomplish better performance byadjusting the radar system to the environment, the objective and inputsexternal to the radar system. The invention accomplishes betterperformance by adapting the radar system under software control.

The radar sensing system of the present invention may utilize aspects ofthe radar systems described in U.S. Pat. No. 9,575,160 and/or U.S. Pat.No. 9,599,702, and/or U.S. patent application Ser. No. 15/416,219, filedJan. 26, 2017, and/or Ser. No. 15/292,755, filed Oct. 13, 2016, and/orU.S. provisional applications, Ser. No. 62/382,857, filed Sep. 2, 2016,and/or Ser. No. 62/381,808, filed Aug. 31, 2016, which are all herebyincorporated by reference herein in their entireties.

As illustrated in FIG. 1, there may be multiple radars (e.g., 104 a-104d) embedded into an automobile. Each of these could employ the ideascontained in the present invention. FIG. 1 illustrates an exemplaryradar system 100 configured for use in a vehicle 150. In an aspect ofthe present invention, a vehicle 150 may be an automobile, truck, orbus, etc. As illustrated in FIG. 1, the radar system 100 may compriseone or more transmitters and one or more virtual receivers 104 a-104 d,control and processing module 102 and indicator 106. Otherconfigurations are also possible. FIG. 1 illustratesreceivers/transmitters 104 a-104 d placed to acquire and provide datafor object detection and adaptive cruise control. The radar system 100(providing such object detection and adaptive cruise control or thelike) may be part of an Advanced Driver Assistance System (ADAS) for theautomobile 150.

A radar system operates by transmitting a signal and then listening forthe reflection of that signal from objects in the environment. Bycomparing the transmitted signal and the received signal, estimates ofthe range to different objects, the velocity of different objects andthe angle (azimuth and/or elevation) can be estimated.

There are several different types of signals that transmitters in radarsystems employ. A radar system may transmit a continuous signal or apulsed signal. In a pulsed radar system, the signal is transmitted for ashort time and then no signal is transmitted. This is repeated over andover. When the signal is not being transmitted, the receiver listens forechoes or reflections from objects in the environment. Often a singleantenna is used for both the transmitter and receiver and the radartransmits on the antenna and then listens to the received signal on thesame antenna. This process is then repeated. In a continuous wave radarsystem, the signal is continuously transmitted. There may be an antennafor transmitting and a separate antenna for receiving. One type ofcontinuous wave radar signal is known as frequency modulated continuouswave (FMCW) radar signal. In FMCW the transmitted signal is a sinusoidalsignal with varying frequency. By measuring the time difference betweenwhen a certain frequency was transmitted and when the received signalcontained that frequency the range to an object can be determined.

A second type of continuous wave signal used in radar systems is a phasemodulated continuous wave (PMCW) signal. In this type of radar system,the transmitted signal is a sinusoidal signal in which the phase of thesinusoidal signal varies. Typically, the phase during a given timeperiod (called a chip period or chip duration) is one of a finite numberof possible phases. A spreading code consisting of sequence of chips,(e.g., +1, +1, −1, +1, −1, . . . ) that is mapped (e.g., +1→0, −1→π)into a sequence of phases (e.g., 0, 0, π, 0, π, . . . ) that is used tomodulate a carrier to generate the radio frequency (RF) signal. Thespreading code could be a periodic sequence or could be a pseudo-randomsequence with a very large period so it appears to be a nearly randomsequence. The spreading code could be a binary code (e.g., +1 or −1).The resulting signal has a bandwidth that is proportional to the rate atwhich the phases change, called the chip rate, which is the inverse ofthe chip duration. By comparing the return signal to the transmittedsignal the receiver can determine the range and the velocity ofreflected objects.

There are several ways to implement a radar system. One way, shown inFIG. 2A uses a single antenna 202 for transmitting and receiving. Theantenna is connected to a duplexer 204 that routes the appropriatesignal from the antenna to the receiver (208) or routes the signal fromthe transmitter 206 to the antenna 202. A control processor 210 controlsthe operation of the transmitter and receiver and estimates the rangeand velocity of objects in the environment. A second way to implement aradar system is shown in FIG. 2B. In this system, there are separateantennas for transmitting (202A) and receiving (202B). A controlprocessor 210 performs the same basic functions as in FIG. 2A. In eachcase, there may be a display to visualize the location of objects in theenvironment.

A radar system with multiple antennas, transmitters and receivers isshown in FIG. 3. Using multiple antennas allows a radar system todetermine the angle (azimuth or elevation or both) of targets in theenvironment. Depending on the geometry of the antenna system differentangles (e.g., azimuth or elevation) can be determined.

The radar system may be connected to a network via an Ethernetconnection or other types of network connections 314. The radar systemwill have memory (310, 312) to store software used for processing thesignals in order to determine range, velocity and location of objects.Memory can also be used to store information about targets in theenvironment.

A basic block diagram of a PMCW system with a single transmitter andreceiver is shown in FIG. 4. The transmitter 400, as shown in FIG. 4,consists of a digital signal generator 410, followed by adigital-to-analog converter (DAC) 420. The output of the DAC followed isup converted to a RF signal and amplified by the analog processing 430unit. The result is then used as the antenna 440 input. The digitalsignal generator generates a baseband signal. The receiver, as shown inFIG. 4, consists of a receiving antenna 460, an analog processing unitthat down amplifies the signal and mixes the signal to baseband 470.This is followed by an analog-to-digital converter (ADC) 480 and thendigital baseband processing 490. There is also a control processor (notshown) that controls the operation of the transmitter and receiver. Thebaseband processing will process the received signal and may generatedata that can be used to determine range, velocity and angle.

Radars must operate in various environments. For example, an automotiveradar must operate in urban areas, suburban areas, rural areas, rain,snow, deserts, parking lots, garages, construction zones, to name a few.Depending on the installation location of the radar in an automobile,the transmitted signal might be reflected off of parts of theautomobile. For example, reflections from a bumper in the automobilemight create very strong self-interference. The set of environments anautomobile is expected to operate in is extensive. Depending on theenvironment different types of signals might be used. A radar signalappropriate for one environment will not be the best signal to use in adifferent environment. The receiver processing used will also depend onthe environment. The environment might be determined from the radaritself but also could be obtained by the radar from external sources(e.g., other vehicles, cellular networks, GPS).

In addition to operating in multiple environments, radar systems mayhave different performance objectives. Range resolution, maximumunambiguous range, Doppler resolution, angular resolution, and field ofview are some of the objectives of a radar system. The smallestseparation of two objects, such that they are recognized as two distinctobjects by a radar, is known as the range resolution of the radar. Therange resolution is inversely proportional to the bandwidth of thetransmitted signal. A short-range radar (SRR) might provide a rangeresolution that is sub-meter (e.g., less than 5 cm) but only fordistances from 0 to less than 30 meters. A long-range radar might have amuch larger range resolution. Another performance measure is the maximumunambiguous range, D_(u). This is the maximum distance of an object suchthat the distance can be correctly (unambiguously) determined from thereceived (reflected) signal. If the delay of the reflected signal can beconfused with another (shorter) delay due to the period of thetransmitted signal, then the distance to the object cannot beunambiguously determined. A long-range radar (LRR) might have a maximumunambiguous range out to several hundred meters whereas a SRR might havean unambiguous range out to several tens of meters.

Doppler resolution refers to the capability of a radar to discriminatethe velocity of different targets. There is a maximum Doppler shift thata radar can determine without ambiguity. This is known as the maximumunambiguous velocity. A radar system using multiple antennas candetermine the angle of a target relative to some reference in either thehorizontal plane (azimuth) or the elevation angle (angle relative to thehorizontal plane). A set of angles for which a radar can detect anobject is called the field of view. Generally, with a fixed number ofantennas, a large field of view would result is less angular resolutionwhile a narrow field of view can provide better angular resolution. Withcertain antenna configurations, the elevation angle of an object can bedetermined.

The description herein includes a radar system in which there are N_(T)transmitters and NR receivers N_(T)×N_(R) virtual radars, one for eachtransmitter-receiver pair. For example, a radar system with eighttransmitters and eight receivers will have 64 pairs or 64 virtual radars(with 64 virtual receivers). When three transmitters (Tx1, Tx2, Tx3)generate signals that are being received by three receivers (Rx1, Rx2,Rx3), each of the receivers is receiving the transmission from each ofthe transmitters reflected by objects in the environment. Each of thereceivers is receiving the sum of reflected signals due to all three ofthe transmissions at the same time. Each receiver can attempt todetermine the range and Doppler of objects by correlating with delayedreplicas of the signal from one of the transmitters. The physicalreceivers may then be “divided” into three separate virtual receivers,each virtual receiver correlating with a replica of one of thetransmitted signals. In a preferred radar system of the presentinvention, there are 1-4 transmitters and 4-8 receivers, or morepreferably 4-8 transmitters and 8-16 receivers, and most preferably 16or more transmitters and 16-64 or more receivers.

As mentioned earlier, there are various types of signals used in radarsystems. A pulsed radar transmits a signal for a short duration of timethen turns off the transmitter and listens for reflections. A continuouswave radar transmits a continuous signal. One type of continuous waveradar signal is known as frequency modulated continuous wave (FMCW)signal. The frequency of this signal is varied from some low frequencyvalue to a high frequency value over some time interval and thenrepeats. Another type of continuous wave radar signal is known as phasemodulated continuous wave (PMCW). The phase of the transmitted signal isvaried in PMCW. Often the variation of the phase is according to aspreading code. The spreading code may be binary (e.g., +1 and −1) inwhich case the phase of the transmitted signal at any time takes on oneof two possible values (e.g., 0 and π radians). Spreading codes withmore than two levels can also be used. Often the code repeats after acertain duration in time duration, sometimes called the pulse repetitioninterval (PRI). Various types of spreading codes can be used. Theseinclude pseudorandom binary sequence (PRBS) codes also calledm-sequences, almost perfect autocorrelation sequences (APAS), Golaycodes, constant amplitude zero autocorrelation codes (CAZAC) also knownas Frank-Zadoff-Chu (FZC) sequences, as well as many other codes thatcan be used. In a radar system with a single antenna, a single spreadingcode is used. The autocorrelation of this single code determines thecapability of the radar to estimate the range (range resolution andmaximum unambiguous range). Codes with good autocorrelation propertiesinclude Barker sequences, m-sequences, FZC sequences, and Golay codes.These codes have small sidelobes (the off-center autocorrelation). Codesthat have ideal autocorrelation (e.g., Golay codes, CAZAC) can haverange sidelobes in the presence of non-zero Doppler shift that willlimit the detectability of far targets in the presence of near targets.

In a multiple-input, multiple-output (MIMO) system, there are multipletransmitters that operate simultaneously. Each transmitter uses aspreading code and thus multiple codes are needed, one for eachtransmitter. In this case (multiple transmitters), codes that have goodautocorrelation, as well as good cross correlation properties aredesirable. Generally, the better the autocorrelation of codes, the worsethe cross correlation properties.

FIG. 5 shows a baseband signal which has a period of L_(C)=31. The chipsin this example are from a maximal length sequence (m-sequence) oflength L_(C)=31 generated by an exemplary shift register of length 5.Note that the signal repeats every L_(C) chips or L_(C)T_(C) seconds.The pulse repetition rate is R_(PR)=1/(L_(C)T_(C)). The transmittedsignal is generated from the baseband signal by modulating the basebandsignal onto a carrier frequency to generate a radio frequency signal.

As illustrated in FIG. 4, the received signal is down-converted to acomplex baseband signal via an RF front end analog signal processing470. The analog signal processing involves amplification, mixing with alocal oscillator signal, and filtering. The mixing is with twosinusoidal signals that are 90 degrees out of phase (e.g., cosine andsine or in-phase and quadrature-phase signals). After down conversion,the complex analog baseband signal is converted to a complex basebanddigital signal by using analog-to-digital converters (ADCs) 480. Thecomplex baseband digital signal (output by the ADCs 480) is then theinput to a digital processing unit 490. The digital processing unit 490performs correlations or matched filtering. The correlators multiply thereceived complex baseband signal by a delayed replica of the basebandtransmitted signal and then the result is accumulated over a certaintime interval. A bank of correlators where each correlator has adifferent delay used for the replica of the baseband transmitted signalwill produce a set of correlations that correspond to different rangesof objects. In essence, a correlator that has a particular delay of thebaseband transmitted signal is looking for the presence of a reflectionfrom an object at a distance corresponding to the particular delay forthe particular correlator, and for which the round-trip delay is thedelay used for the baseband transmitted signal.

A matched filter is a device that produces all correlations for allpossible delays. That is, the output of the matched filter at a giventime corresponds to a correlation with a given delay applied to thetransmitted signal when doing the correlation. The matched filterprovides all possible correlations. Note that the matched filter shouldproduce a complex output because the input is complex. Alternatively,there could be a filter for the real part of the input and a filter forthe imaginary part of the input. A matched filter can also beimplemented by a fast Fourier transform (FFT) of the received complexbaseband signal and the corresponding transmitted signal, multiplyingthe results, and then taking an inverse fast Fourier transform (IFFT).

FIG. 5 illustrates a baseband signal which has a period of L_(C)=31. Thechips in this example are from a maximal length sequence (m-sequence) oflength L_(C)=31 generated by an exemplary shift register of length 5.Note that the signal repeats every L_(C) chips or L_(C)T_(C) seconds.The pulse repetition rate is R_(PR)=1/(L_(C)T_(C)). The transmittedsignal is generated from the baseband signal by modulating the basebandsignal onto a carrier frequency to generate a radio frequency signal.

FIG. 6 shows the real part of the output of a matched filter due to thetransmitted baseband signal shown in FIG. 5. Here it is assumed theradar started to transmit at time 0 and there is no delay between thetransmitter and receiver. That is, there is an object at distance 0. Thematched filter output before a full period of the signal is transmittedgenerates partial correlations. That is, it correlates with only aportion of the code because only a portion of the code has beentransmitted. Only after the entire period of the code has beentransmitted does the correlation reach a peak. In continuous operation,an object that has a delay of one period of the spreading code willappear to have the same delay as an object at distance 0. Thus, a radarusing this system cannot determine whether the delay is 0, one period ofthe spreading code, two periods of the spreading code, and so on.Therefore, the maximum unambiguous range in this case corresponds to atmost one period of the spreading code. A longer spreading code willyield a larger maximum unambiguous range. A delay of τ corresponds to arange of τc/2 where c is the speed of light. The factor of two isbecause the delay corresponds to the round-trip time from the radar tothe target and back to the radar. Here the assumption is that thetransmitter and receiver are approximately co-located.

FIG. 7 illustrates the real part of the output of the matched filterwhen there are two objects that have a differential range delay of 2chip durations. The filter output shows two distinct peaks in the outputof the matched filter.

For PMCW radar systems that utilize nonideal spreading codes andcorrelate over a certain time interval, the autocorrelation is notideal. That is, the sidelobes are not zero. The sidelobes of a neartarget can mask the peak of the correlation for a far object or targetbecause the signal from the near object or target is far stronger thanthe signal from the far object or target.

Range Estimation

FIG. 8 illustrates the case where the differential round trip delaybetween two targets is one chip duration. In this case, two objectscannot be distinguished and thus the range resolution of this wouldcorrespond to the differential distance corresponding to a duration ofhalf (½) a chip. If Tc denotes the chip duration and Lc denotes thenumber of chips in one period of the transmitted sequence, then the rateat which the sequence is repeated is Rpr=1/(L_(C)T_(C)), which issometimes referred to as the pulse repetition rate even though this is acontinuous type of signal. If c denotes the speed of light, then therange resolution is given by:

D _(R)=(T _(C)/2)c=c/(2R _(PR) L _(C)).

If a signal repeats every T_(PR) or at rate R_(PR), then the maximumunambiguous range D_(U) is:

D _(U) =cT _(PR)/2=(c T _(C) L _(C))/2=c/(2R _(PR)).

Two targets separated by the maximum unambiguous range will appear tothe radar systems as being at the same range. This is sometimes calledrange aliasing. If the chip duration, T_(C), is decreased, then therange resolutions would improve proportionally. However, changing thechip duration changes the bandwidth, which might be limited byregulations. If there are 31 chips per period of the spreading code,there are at most 31 different ranges that can be distinguished. As anexample, if T_(C)=10 nanoseconds (a chiprate of 100 Mchips/second), thenthe range resolution would be limited to 1.5 meters. That is, twoobjects separated by less than 1.5 m would cause reflected signals to beless than a chip duration apart in delay. For this example, the maximumunambiguous range would be 46.5 m. That is, an object at a distance of46.5 m would cause a reflected signal to have a delay exactly equal tothe period of the signal and thus would appear as an object at adistance of 0 m. A longer spreading code would provide for a largerunambiguous range. For example, a spreading code of length 1023 wouldprovide a maximum unambiguous range of about 1,534 m.

Velocity Estimation

Another goal of an exemplary radar system is to estimate thedifferential velocity between the radar system and a target. Becausetargets in the environment, or the radar itself, are moving, the signalreflected from an object will not have the same frequency as thetransmitted signal. This effect is known as the Doppler Effect and canbe used to determine the relative velocity of targets in theenvironment. Suppose the differential (radial) velocity of the targetrelative to the radar system is Δv and the carrier frequency is f_(C).Then, the Doppler frequency shift is f_(D)=2ΔV f_(C)/c. This is becausethere is a Doppler shift of ΔVf_(C)/c between the radar transmitter andthe target and then an additional ΔVf_(C)/c Doppler shift of thereflected signal from the target to the radar receiver. For example, acarrier frequency of 79 GHz with a differential velocity of 300km/hour=83.3 m/s would result in a frequency shift of about 44 kHz. Afrequency shift of f_(D) corresponds to a differential velocity ofΔV=(f_(D))c/(2 f_(C)).

Suppose that a signal, for example an m-sequence, is repeated N times.This is called a scan. The period of the signal is L_(C)T_(C). The timeduration of the scan is N*L_(C)T_(C). During each repetition, acorrelation with a spreading code with a given delay (e.g.,corresponding to the delay with a given target) is calculated. Thiscorrelation calculation generates a complex number for a given delay andthis repeats N times during a scan. The N complex numbers can be used todetermine the Doppler frequency shift at the given delay. In the absenceof Doppler frequency shift the complex correlation values will beconstant. In the presence of a Doppler shift the complex correlationvalues will rotate. The rate of rotation will be related to the Dopplerfrequency. FIG. 9 illustrates the real and imaginary parts of thematched filter output when there is a Doppler shift. FIG. 10 illustratesthe complex values at the peak correlation outputs. As can be seen, thematched filter output is rotating around a circle. The rate of rotationis a measure of the Doppler frequency. Knowing the Doppler frequencyallows a calculation of the relative velocity of a target.

One way to estimate the Doppler frequency is to use a fast Fouriertransform (FFT) on the complex samples. With this approach to estimatingthe frequency shift due to Doppler, with N points as the input to theFFT, there will also be N frequency points generated. The frequencyresolution possible is over the range of frequencies from a negativefrequency of −R_(PR)/2 to a positive frequency +R_(PR)/2 or a range ofR_(PR). Thus, the spacing between frequency points will bef_(R)=R_(PR)/N. This is the frequency resolution. This corresponds to avelocity resolution of:

V _(r) =c R _(pr)/(2f _(c) N).

If the complex correlation samples are produced at a rate ofR_(PR)=1/T_(PR)=1/L_(C)T_(C), then the frequency range that those pointsrepresent is limited to −R_(PR)/2 to +R_(PR)/2. Thus, the maximumunambiguous differential frequencies f_(u) that can be represented isgiven by −R_(pri)/2<f_(u)<+R_(pri)/2. When this is converted tovelocity, the result is that the maximum unambiguous velocity is limitedto values in the interval shown below:

−cR _(PR)/(4f _(C))<V _(U) <+cR _(PR)/(4f _(C)).

Increasing the repetition rate increases the maximum unambiguousvelocities that can be determined. However, increasing the repetitionrate decreases the maximum unambiguous range that can be determined. Theproduct of the maximum unambiguous velocity and maximum unambiguousrange is limited as

−c ²/(8f _(c))<D _(u) V _(u) <c ²/(8f _(c))

which is independent of the various parameters of the transmittedsignal, except the carrier frequency.

The product of the velocity resolution and the range resolution is givenas

D _(r) V _(r) =ĉ2/(4_(FC) L _(C) N)

where L_(C) is the number of chips in a single period of the spreadingcode and N is the number of points in the FFT used to determine thevelocity. For a fixed scan time (L_(C)N T_(C)) and fixed chip durationT_(C), there is a tradeoff between the resolution possible for the rangeand the resolution possible for the velocity. By increasing N anddecreasing L_(C), the velocity resolution improves at the expense ofrange resolution. Similarly, decreasing N and increasing L_(C) willimprove the range resolution at the expense of velocity resolution.

In some systems the signal has L_(C) chips per period but this sequenceis repeated M times and the correlation values are accumulated togenerate a signal complex sample for a given range. The sequence of suchsamples is then used for Doppler processing.

The above illustrates a tradeoff between the maximum unambiguous rangeand the maximum unambiguous velocity that only depends on the carrierfrequency. An increased product of unambiguous velocity and range canonly be obtained if the carrier frequency is decreased. In somecircumstances, it might be desirable to obtain a larger unambiguousrange at the expense of a smaller unambiguous velocity (or vice versa).Thus, a system that can adjust the repetition frequency of the signalwould be able to adjust to different objectives. There is also atradeoff between range resolution and velocity resolution for a givenbandwidth and scan duration. In some situations, it would beadvantageous to have better range resolution while in other cases itwould be beneficial to have better velocity (or Doppler) resolution.Thus, it would be of benefit to be able to adjust the system parametersdepending on the objective function of interest to obtain either thebest range resolution or the best velocity resolution (with a givenfixed time interval for the scan).

As an example, consider a radar system with a desired scan duration(time to produce a velocity estimate) of 0.1 ms (100 scans per second).Suppose the chip rate is fixed at 10⁻⁸ seconds and the carrier frequencyis 79 GHz. A spreading code period of 100 chips would allow 1000repetitions in the scan time. This corresponds to an unambiguous rangeof 150 m and an unambiguous velocity estimate range of (−950 m/s, +950m/s). On the other hand, a spreading code period of 1,000 would allowonly 100 repetitions of the code in the same time. The unambiguous rangewould increase to 1,500 m, while the unambiguous velocity would decreaseto (−95 m/s, +95 m/s).

At the receiver it is necessary to store the complex outputs of thecorrelators for different possible ranges and for different receivers. Asequence of N complex samples needs to be stored for a particular rangeand a particular virtual receiver (a receiver matched to a particularspreading code of a transmitter) in order to determine an estimate ofthe velocity for an object at a particular range. For example, supposethat there are 512 range bins desired to locate potential targets andthe number of repetitions of the code is 1024. This would requirestoring 512×1024 complex numbers with each complex number requiring 4bytes of storage. This would require more than 2 million bytes ofstorage per virtual receiver. If there are 4 transmitting antennas and16 receiving antennas then this would require about 134 Mbytes ofstorage, much more than is practical with current storage limitsintegrated onto a chip. On the other hand, storing this off chip wouldrequire a significant amount of time to transfer data. At a rate of 1600Mbytes/second only about 12 transfers could happen per second. Thenumber of virtual receivers determines the possible angle resolution.More receivers can provide more angular resolution at the expense ofadditional storage or at the expense of worse range or velocityresolution. Thus, the storage restrictions limit either the angularresolution, the range resolution, or the velocity resolution.

In automotive radar systems, there are various objects in theenvironment that reflect the transmitted signals of the radar. Some ofthe objects are stationary objects such as road signs, parked cars,light poles and such. There are numerous such objects that arestationary but since the automobile containing the radar is moving,these objects generate reflected signals with Doppler shift relative tothe transmitted signal. On the other hand, there are objects such asother vehicles which are not stationary in the environment and have adifferent Doppler shift than stationary objects. Often, the stationaryobjects appear as a dense collection of radar returns for differentranges and different angles, whereas nonstationary objects are rathersparse in the environment. These characteristics can be exploited inprocessing the data obtained from the signals received from objects inthe environment.

In addition to the above, interference from other radar systems needs tobe accounted for. Interfering radars could be using the same type ofsignals as the vehicle in which the invention of this patent isinstalled. It is also possible that the interfering radar system isusing a different type of signal (e.g., FMCW vs. PMCW). It would beuseful to be able to mitigate in some way the effect of interferingradar systems. Different types of interference will require differentmitigation techniques. Mitigation of the effects of interfering systemsgenerally will not be ideal and it is often the case that themitigation, while reducing the effect of the interference, will alsodegrade the desired signal in some manner. If no interfering radarsystem is present, then it would be desirable to not employ themitigation technique. As such, it would be desirable to have a radarsystem that can adapt to the environment present.

In a preferred embodiment, the processing of the signals is shown inFIGS. 11a, 11b, 11c, and 11d . FIG. 11a illustrates exemplary processingmodules for a transmitter. A code generator 1102 generates a spreadingcode. The output of the code generator 1102 is modulated with a digitalmodulator 1104 to generate a complex baseband signal. The modulation isaccomplished in two parts. In the first part the code is mapped to acomplex sequence of in-phase and quadrature phase components at thedigital modulator 1104. The result is converted to an analog signal bythe digital-to analog converter (DAC) 1106. The output is further shapedwith a pulse shaper 1108 to generate a complex baseband analog signal.This signal is up-converted with a TX Mixer 1110. An oscillator 1124 isthe other input to the mixer to produce a radio frequency (RF) signal.The oscillator signal is also used at the receiver. This is indicated bythe connection of the oscillator to components in FIG. 11b . The resultof up-conversion is then amplified by a power amplifier 1120 beforetransmission by an antenna 1122. A master clock 1126 is used to controlthe timing of the oscillator and to control the timing of the digitalcircuitry. The master clock 1126 and the oscillator are also shared withthe transmitter circuitry shown in FIGS. 11b and 11c . The output of thedigital modulator 1104 is shared with the receiver so that the receivercan apply interference cancellation. The output of the code generator1102 is shared from the transmitter to receiver so appropriatecorrelation or matched filtering can be applied at the receiver.

FIG. 11b illustrates exemplary analog processing circuitry of thereceiver. Various blocks or modules are illustrated. One or morereceiving antennas are connected to a switch 1142 that connects one ofthe antennas 1140 to a receiver. There can be more than one receiver sothat different antennas can be connected to different receivers. Not allthe antennas need to be connected to a receiver. Because there can bevery strong self-interference from the transmitted signal reflecting offof nearby objects (e.g., a bumper), the analog interference cancellationunit 1146 is employed. A signal from the cancellation unit 1146 can beprovided to the digital processing where additional interferencecancellation can be done. The output of the analog interferencecancellation 1146 is provided to a low noise amplifier 1148. The lownoise amplifier output is mixed down to baseband by an RF mixer thatalso uses the oscillator signal (from FIG. 11a ). The resulting low passcomplex baseband analog signal is filtered (with low pass filter 1152),and further amplified (with gain control 1154) before being converted toa digital signal by an analog-to-digital converter (ADC) 1156. Theresult of the ADC 1156 is fed to digital processing circuitry shown inFIG. 11 c.

FIG. 11c illustrates exemplary digital processing circuitry of thereceiver. Various signal processing blocks or modules are illustrated.First, a saturation detection block 1160 detects whether the ADC inputhas caused the ADC 1156 to saturate. This detection can be used toadjust the gain in the gain control 1154. Next, a change in the samplerate can be performed (1162) to reduce the amount of processingnecessary. After resampling, correction for any mismatch in I, Q gain ornon-orthogonality can be employed (via I/Q Correction module 1164).Additional interference can be cancelled in a digital interferencecanceller 1166. Information from the processing done by the analogcancellation unit 1146 can be used (as shown by the connection from FIG.11b ) by the digital interference cancellation unit 1166. This can moreaccurately (as compared to the analog interference canceller 1146)remove interference from near targets, including the bumper. Furtherinterference cancellation (with large target canceller 1168) can be doneto minimize the effect of sidelobes of a near target on thedetectability of a further target. Interference from other radarsystems, such as an FMCW system, can also be incorporated (such asFMCW/Tone Canceller 1170) into the digital processing. The resultinginformation is stored in a buffer 1174. This allows all digitalprocessing to be suspended temporarily in order to not create unwantedradio frequency interference from the digital processing. Finally, thesignal is processed by correlating with a correlator 1176, with delayedversions of the code from the code generator (1102). The correlator(s)1176 could be implemented in a number of ways including a matched filterand an FFT-based approach. The samples of the output of the correlatoror matched filter (1176) are stored in memory as radar data cubes (RDC),such as RDC1 (1178). The correlation values for different delays,different receivers, and different times are stored in the radar datacube. The information from RDC1 is processed further to determine objectvelocity and angle (e.g., azimuth or elevation or both). The informationfrom the correlators for one scan may be stored in different parts ofthe radar data cube so that data can be written in one part of thememory RDC1 and used for Doppler and angle processing while other partsof the memory corresponding to different scans are being read forDoppler and angle processing. The sizes of these different parts of thememory can be different, corresponding to different performanceobjectives. Further software control of the processing of informationstored in RDC1 may be performed to determine the velocity of targets.

FIG. 11d illustrates the back-end digital processing. The front-endanalog and digital processing, illustrated in FIGS. 11a-c , processesthe received signal and stores the processed information (complexsignals) in the radar data cube 1 (RDC1). The information is related tosignals reflected from objects as a function of time (one of thedimensions) at various distances (a second dimension) and for variousreceivers (a third dimension). Information from various receivers isstored in a common memory. To determine the velocity of an object, aparticular “slice” of the radar data cube is processed. A slice of acube refers to a two-dimensional subset of the data where one of thevariables (either range, time, or receiver) is fixed. Processing canalso be done on the information with the range and Doppler fixed. Inthis case, the data is one dimensional and is known as a skewer. Theslice of RDC1 where range is fixed, and the virtual receiver is fixed,but the sequence of correlation values for different times are varied,can be used to calculate a Doppler shift. By taking the fast Fouriertransform of RDC1, with respect to the time dimension, the Doppler at agiven range, and for a given virtual receiver, can be determined. Thisinformation is stored in radar data cube 2 (RDC2). The Dopplerprocessing (1180) has as input of time samples and performs a Fouriertransform processing (e.g., FFT, DFT or channelizer) to generate Dopplerinformation stored in RDC2 (1182). The time samples can be windowed asneeded or zero padded, depending on the radar system objective and/orexternal inputs. One type of windowing is a rectangular window whichallows for accurately estimating the peak of strong signals at theexpense of poorer sidelobe suppression. A Dolph-Checyshev windowingsupports greater side-lobe suppression to allow detection of weakersignals that would otherwise be hidden by the side-lobes of the strongersignals. The signal samples can also be padded to obtain better Dopplersampling granularity. The window used and the padding employed are fullycontrollable from the control processor. Radar data cube 2 (RDC2) storescomplex samples in three dimensions: range, Doppler, and virtualreceiver.

The next step in processing the data is using the RDC2 information tocalculate the angle of arrival for a particular range and a particularDoppler shift. This is done in angle processor 1184. The resultinginformation is stored in RDC3 which has dimensions corresponding torange, Doppler, and angle (azimuth and/or elevation). The angle ofarrival processing (1184) does a beam forming type of algorithm on theRDC2 data as a function of the virtual receiver. The angle processordoes beam forming using a steering vector to weight the differentreceiver outputs and combine the weighted outputs. The beam forming usedwill depend on the particular set of antennas employed, as configured bythe control processor. Aspects of such beam forming are also discussedin U.S. patent application Ser. No. ______, filed concurrently with thepresent patent application, and titled SOFTWARE DEFINED AUTOMOTIVE RADAR(Attorney Docket UHN01 P-119), which is hereby incorporated by referenceherein in its entirety.

Since the antennas are switchable, the angle of arrival calculation isdependent on the selection of antennas. Storage of information in RDC2and RDC3 can be implemented with a first in, first out (FIFO) bufferwhere all the information associated with a particular scan (e.g.,range, Doppler and virtual receiver) are not necessarily storedsimultaneously but are being written into the FIFO while otherinformation is being read out.

The analog processing of the received signal from the antenna to the ADCis called the analog front end. The processing of digital signals fromthe ADC to RDC1 is called the digital front end. The control of theseoperations is done by a processor as described in the above incorporatedU.S. patent application Ser. No. ______, filed concurrently with thepresent patent application and titled SOFTWARE DEFINED AUTOMOTIVE RADAR.

The same processor controls the further processing of signals from RDC1to RDC3 and then post RDC3 processing. This processing of digitalsignals from the RDC1 to generate Doppler information and angleinformation, along with the range information already determined, whichis stored in radar data cube 3 (RDC3), is called the digital back end.

As mentioned above, the signals to be used for transmitting, and thereceiver processing to be employed, depend on a number of differentfactors including the environment (e.g., an urban area, suburban area,parking lot, garage, construction zone etc.). Different, changingobjectives for the radar system might be desired (e.g., small rangeresolution, small velocity resolution, small angular resolution, etc.).Different types of interference might be present in the radar system(e.g., FMCW radars, PMCW radars, etc.). Therefore, it is desirable to beable to dynamically adapt the radar to different environments, differentperformance objectives, different external inputs, and different typesof interference. Embodiments of the present invention provide for asoftware controllable adaptable radar system.

Radar Data Compression

In a radar system, Doppler processing typically comprises performing afast Fourier transform (FFT) using a sufficiently long time series ofcomplex data at the input to the FFT. This Doppler processing isperformed independently on multiple time series, captured simultaneouslyby multiple virtual receivers for multiple range bins. However, theentire time series must be available before FFT processing can begin.This requires partial time series to be stored in memory as the pointsof the time series are captured, which can result in a large amount ofmemory being used. To enable longer scans, or scans with more virtualreceivers, or more range bins, and using a limited amount of memory, itis desirable to first compress the time series as they are captured,then store the compressed representations in memory, and once they arefully captured, decompress them prior to performing Doppler processingon them. The compression should be lossless to avoid introducingcompression artifacts into the data. There are various losslesscompression algorithms that can be employed. For example, MPEG4-audiolossless coding (MPEG4-ALS) is one compression standard that has variousparameters that can change the amount of compression and change thecomplexity of the algorithm. In MPEG4-ALS, data is the input to apredictor. The difference between the predicted value and the actualvalue is compressed using a form of entropy coding. Data may beoptionally converted from complex in-phase and quadrature (I/Q) formatto phase angle and magnitude format prior to the prediction step. Afterprediction, residual values (the difference between the predicted valueand the actual value) are compressed using an arithmetic or entropyencoding algorithm. Within a given range bin, predictors predict samplesof data based on the value of samples from adjacent virtual receivers(to either side of the sample being predicted), and from previous timesamples for the same virtual receiver. Inter-range bin prediction mayalso be used. The compression of data that is stored in RDC1 (for laterDoppler processing) is controlled by software and can be adapted toachieve certain objectives, such as processing time and memoryrequirements.

Compensating for Doppler Shift:

Doppler shift has an adverse effect on a radar system's ability tocorrelate a received signal with various delayed or shifted versions ofthe transmitted signal to determine range. Because the phase of thereceived signal rotates due to Doppler shift, the magnitude of the peakcorresponding to the delay of a target (so called zero-shift) decreaseswith increasing Doppler. Also, the average magnitude of thenon-zero-shift “sidelobes” increases with increasing Doppler. The effectis that the SNR for the target in question is reduced and the SNR forall targets in all other range bins (non-zero shifts) decreases becausethe noise or interference from one target is now spread over differentrange bins. Naturally, largest target(s) cause the largest sidelobes.The present invention incorporates a method and device for compensatingfor Doppler shift, comprising:

-   -   a. Identifying a set of the largest (highest received signal)        targets;    -   b. Estimating the Doppler velocity for the largest targets using        a median, a weighted arithmetic mean, or a weighted geometric        mean of the Doppler for several adjacent range bins that        correspond to the target;    -   c1. Calculating the phase shift, φ₁, from one complex correlator        input sample to the next complex correlator input sample,        corresponding to the estimated Doppler velocity; and/or    -   c2. Calculating the phase shift, φ₂, from one complex correlator        output sample to the next complex correlator output sample,        corresponding to the estimated Doppler velocity; and    -   d. Derotating the Nth complex (pre or post correlator) sample by        N*φ₁ or N*φ₂.

A processor controls the identification of the set of largest targets.In the case of a single large target, no additional memory is required.In the case of two or more large targets, multiple (full or partial)RDC1 cubes are required. The processor also controls the estimation ofthe Doppler of the large target(s).

On Demand Multi-Scan Micro-Doppler:

In a radar system, achieving high Doppler resolution requires longscans. Practical limitations on the length of a scan, such as memoryusage, and the desire to obtain frequent updates from the radar, limitthe maximum achievable Doppler resolution in a single scan. Typicalscans may be able to achieve Doppler resolutions of up to 0.1meters/second. A system and methods for achieving high resolutionDoppler measurements for selected targets by combining information frommultiple scans is described in detail in U.S. Pat. No. 9,599,702.

While memory considerations prevent saving the entire raw radar datacube (‘RDC1’) from multiple scans, it is possible to identify and saveonly a subset of the data cube (e.g., a small subset of the range bins),the subset comprising a time series of complex valued samples of thesignal from each virtual receiver for the range bin, or bins, ofinterest.

Once the data for a particular range bin (or bins) has been saved tomemory for multiple consecutive scans, using the same scan parameters,micro-Doppler post processing can be performed, comprising the steps ofconcatenating or joining or linking each time series, optionallyinserting zeros in the time series to compensate for any delays betweenscans, performing a fast Fourier transform (FFT) on each time series toconvert them from the time domain to the Doppler frequency domain (oralternatively using a channelizer), followed by any angle-of-arrivalprocessing (e.g., beamforming or angle super-resolution) that may bedesired. The decision about when to perform such multi-scan processingand for which range bins to process is controlled a processor.

Fully Pipelined Architecture:

The present invention provides a fully reconfigurable, pipelined radararchitecture, which allows the user to perform different radar scans fordifferent use case scenarios while keeping the memory requirementsfairly small. Aspects of such pipelined radar architecture are describedin the above incorporated U.S. patent application Ser. No. ______, filedconcurrently with the present patent application and titled SOFTWAREDEFINED AUTOMOTIVE RADAR. The architecture comprises:

-   1. A programmable PRN generator for non-periodic (PRBS based codes)    and periodic codes (with support for Hadamard Matrix). The PRN    generator supports switching of periodic codes for each FFT point as    well as constructing PRBS sequences based on fully configurable HW    generated PRBS sequences.-   2. Fascia reflection self-Interference mitigation. Self-interference    mitigation is discussed in U.S. patent application Ser. No. ______,    filed concurrently with the present application and titled VEHICULAR    RADAR SYSTEM WITH SELF-INTERFERENCE CANCELLATION (Attorney Docket    UHN01 P-121), which is hereby incorporated by reference herein in    its entirety.-   3. FIR decimation (Reduce frequency from 2 GHz to 75 MHz)/FIR range    walking/FMCW canceler.-   4. An FFT based correlator for range bins.-   5. A Correction engine for successive cancelation as well as    amplitude and phase correction.-   6. Compression/de-compression of a radar data cube (time samples),-   7. FFT channelizers or Doppler processing.-   8. Angle of arrival computation (delay and sum/FFT)-   9. Decimation to store only relevant information out of the radar    data cube.

Only items 4 and 5 require a full radar data cube (RDC1). The stepsafterwards require a much smaller temporary storage since thecomputations are done more or less in flight. The processing of theradar data cube is in general done faster compared to the accumulationof the new radar data cube to ensure minimal memory overhead. Thecontrol processor controls these operations.

Ghost Interference Removal:

In a PMCW radar, mitigation of the adverse effects of interference fromother PMCW radars is difficult because, without knowledge of the exactcode and carrier frequency used by the interfering radar, there is nostraightforward way to suppress the interference. The spectrum spreadingcaused by the interfering radar's use of pseudo-random code sequencesresults in an elevated noise floor, which in turn reduces a radar'sability detect weak targets.

The present invention proposes a method and device to isolate andsuppress the interference from another PMCW radar using periodicspreading codes, comprising the steps of: using a first periodic codewith the same period as the interfering PMCW radar (but not necessarilythe same code, or the same carrier frequency), capturing a first N timesamples (aka: FFT points), then repeating with a second periodic codewith the same period as first periodic code, and capturing a second Ntime samples, optionally repeating this process one or more additionaltimes for a total of K times, and then performing Doppler processing oneach of the K sets of N time samples to compute K frequency spectrums.The control processor compares the frequency spectrums and identifiesthe peaks (the “inconsistent signals”) whose magnitude varies across theK frequency spectrums and the peaks (the “true signals”) whose magnituderemains constant (or nearly so) across the K frequency spectrums. Thecontrol processor modifies or instructs the hardware to modify allcaptured time samples to remove frequencies that correspond to theinconsistent signals. Finally, a single FFT is performed over all K*Nmodified samples. This technique has been shown to lower the noise floorby 20 dB or more. Methods for mitigating interference from other PMCWradars is discussed in U.S. patent application Ser. No. 15/416,219,filed Jan. 26, 2017, which is hereby incorporated by reference herein inits entirety.

The control processor identifies the existence of one or moreinterfering radars. The control processor also controls the type ofspreading codes being used (the period, the type, etc.). Lastly, thecontrol processor also controls the choice of K and N used forinterference estimation.

Memory Reduction by Beamforming and Decimation/Sparsification:

The present invention provides a method and device for reducing theamount of post Doppler processing data, in a phased array radar system,that must be stored to memory for performing subsequent processing. Themethod comprises the steps of:

-   -   Performing spatial windowing and beamforming (e.g., delay and        sum) on one or more input (complex) sample vectors from RDC2 for        a given range and Doppler for various virtual receivers to        produce output complex sample vectors (RDC3) for the        corresponding range and Doppler and angle.    -   The control processor identifies a region of samples in RDC3. In        a preferred embodiment, this region corresponds to a band of low        absolute velocity that includes ground clutter.    -   Samples of RDC3 in the identified band are stored in a separate        memory buffer called a static slice. The samples in the        identified band are tagged as being included in the static        slice. The complete set of RDC3 samples are processed by a        decimator/sparsifier.    -   For each untagged sample in RDC3, the decimator/sparsifier        compares the magnitude of the sample to one or more thresholds        configured by the control processor. Depending on the outcome of        the comparison, a set of samples, including the sample, are        stored in one of one or more distinct memory buffers.        Preferably, the set of samples are samples with similar Doppler,        range and/or angle (azimuth and/or elevation). In the preferred        embodiment, the set includes all samples with the same range and        Doppler. These buffers are called the sparsified RDC3 (sRDC3).        In a preferred embodiment, different thresholds may be        configured for different range bins. In another preferred        embodiment, the thresholds are determined by analyzing        histograms of RDC3 sample magnitudes. Different histograms may        be computed for different subsets of RDC3 (e.g., one histogram        per range bin).    -   The samples stored in the static slice or the sparsified RDC3        (sRDC3) may be stored as complex numbers (real and imaginary        part), magnitude only, or both. Which mechanism to store is        determined by the control processor.

The above steps of processing are controlled by the control processor inorder to achieve the performance objectives.

Asynchronous, Parallel, Memory Efficient MUSIC Engine:

The present invention provides a method and device for performingadaptive on-demand super resolution angle-of-arrival (AoA) processing ona subset of the range, Doppler, angle space (i.e., a subset of RDC3),comprising the steps of:

-   -   Using a control processor to analyze the static slice and sRDC3        to identify regions of interest. In a preferred embodiment, the        region of interest is a local maximum of the magnitude of the        samples. The control processor tracks regions of interest over        time including multiple scans.    -   Using a control processor to choose a subset of range, Doppler,        angle space based on past and current samples of the static        slice and/or sRDC3 in the regions of interest, in which to        perform super resolution angle of arrival processing.    -   Using a control processor to select a subset of the range bins        of RDC1 on which to perform Doppler processing. In the preferred        embodiment, the Doppler processing is performed by a        channelizer. Using a control processor to select a subset of the        Doppler bins (channels) to perform super resolution processing.    -   Using a control processor to configure a MUSIC engine to provide        super resolution processing on the subset of range, Doppler, and        angle space. In preferred embodiment, the configuration includes        spatial smoothing steps, parameters for singular value        decomposition (SVD) calculation (e.g., a maximum number of        iterations and precision threshold), an estimated number of        signal eigenvectors, and steering vector matrix). In the        preferred embodiment, the control processor configures the MUSIC        engine by providing commands and parameters through a FIFO.    -   Using a MUSIC (MUltiple Signal Classification) Engine configured        by the control processor to determine location of peaks in the        angular dimension for the specified subset of range, Doppler,        and angle space, comprising the steps of:        -   Calculating a sample covariance matrix from one or more            samples of input data.        -   Performing spatial smoothing on the covariance matrix.        -   Calculating the singular value decomposition of the            covariance matrix.        -   Using the singular values to estimate the number of signals.        -   Using a sub-matrix of the left unitary matrix (representing            the noise subspace) to compute the MUSIC spectrum over a            specified range of angles.        -   Writing to an output FIFO a list of angles corresponding to            peaks of the MUSIC spectrum occurring in the specified range            of angle.

Compressing Range Bins Dynamically and Adaptively (Variable Range Bins):

In case of a PMCW-based radar system, range bins are used to identifyhow far objects are from the radar. The range bin resolution is usuallylinear, which means if the range bin resolution is 0.1 m, then 900 rangebins are required for a distance of 10-100 m. This results in a largeradar cube overhead. The larger the distance, the larger can be therange resolution. The range bins can be compressed, assuming for examplethat the range resolution can be 1 percent of the distance, which meansat 10 m the range resolution is 0.1 m, at 20 m it is 0.2 m, at 30 m itis 0.3 m, and so on. If variable range bins are used, several range binscan be combined to a single range bin when the object is far away,thereby effectively reducing the total number of required range bins.

This approach can also be used to reduce the number of total range binsif object locations are known or object positions are being tracked.Assume for example, that the range between 10-100 m is using a rangeresolution of 2.5 m, which implies 36 range bins. And as soon as a rangebin contains objects to be tracked, only that quadrant is used, withhigher resolution range bins. The present invention uses a controlprocessor to configure the resolution around tracked objects with muchhigher resolution compared to the areas without objects.

The system thus has reduced memory requirements by compressing severalrange bins into a single range bin using a configurable variable rangebin parameter on a per range bin basis. Care is needed prior toaggregating range bins as the SNR will be negatively impacted. For closeobjects and near empty ranges, this is likely a good trade off. Thecontrol processor controls the ranges and resolutions that arecorrelated with by the pipeline processing.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

1. A radar sensing system for a vehicle, the radar sensing systemcomprising: a plurality of transmitters configured for installation anduse on a vehicle, wherein the transmitters are configured to transmitmodulated radio signals; a plurality of receivers configured forinstallation and use on the vehicle, wherein the receivers areconfigured to receive radio signals, and wherein the received radiosignals are transmitted radio signals reflected from an object in theenvironment; wherein each transmitter of the plurality of transmitterscomprises a digital processing unit, a digital-to-analog converter, ananalog processing unit, and a transmit antenna; wherein each receiver ofthe plurality of receivers comprises a receive antenna, an analogprocessing unit, an analog-to-digital converter, a digital front endprocessing unit, and a digital back end processing system; a memory; acontrol unit configured to select an operating mode for the radarsensing system and to modify the plurality of transmitters and theplurality of receivers based on a current environment condition andoperation status, and based on one of a best range resolution and a bestvelocity resolution; wherein range information data produced by thedigital front end processing unit of at least one receiver of theplurality of receivers is stored in the memory and then processed by thecorresponding digital back end processor of the at least one receiver ofthe plurality of receivers, as directed by the control unit; and whereinthe range information data includes range information of objects in theenvironment, and wherein the range information data is stored in thememory for different receivers and for different scans, and wherein theprocessing of the range information data is controlled by the controlunit.
 2. The radar sensing system of claim 1, wherein the control unitis configured to modify at least one of an operation and a mode of atleast one of (i) a digital processing unit of at least one transmitterof the plurality of transmitters, (ii) a digital-to-analog converter ofat least one transmitter of the plurality of transmitters, (iii) ananalog processing unit of at least one transmitter of the plurality oftransmitters, and (iv) a transmit antenna of at least one transmitter ofthe plurality of transmitters, and wherein the control unit isconfigured to modify at least one of an operation and a mode of at leastone of (i) a receive antenna of at least one receiver of the pluralityof receivers, (ii) an analog processing unit of at least one receiver ofthe plurality of receivers, (iii) an analog-to-digital converter of atleast one receiver of the plurality of receivers, (iv) a digital frontend processing unit of at least one receiver of the plurality ofreceivers, and (v) a digital back end processing system of at least onereceiver of the plurality of receivers.
 3. The radar sensing system ofclaim 1, wherein the data stored in the memory, before Dopplerprocessing by the digital back end processor, is compressed, ascontrolled by the control unit.
 4. The radar sensing system of claim 3,wherein the compression used is MPEG4-audio lossless coding.
 5. Theradar sensing system of claim 3, wherein before the Doppler processing,a window function, controlled by the control unit, is applied to asequence of samples for a given range and receiver, and wherein theplurality of receivers includes virtual receivers.
 6. The radar sensingsystem of claim 1, wherein after the range information data is stored inthe memory, a sequence of samples, as selected by the control unit, ispadded with zero valued samples prior to Doppler processing asconfigured by the control unit.
 7. The radar sensing system of claim 1,wherein the control unit is operable to configure at least one receiverof the plurality of receivers to process the range information datastored in the memory, and wherein the at least one receiver isconfigured to: identify a set of objects with a highest received signalstrength; estimate a Doppler velocity for the objects using one of amedian, weighted arithmetic mean, and weighted geometric mean ofcorresponding samples for different range bins associated with theobject; calculate one of a first phase shift, from one complexcorrelator input sample to a next complex correlator input sample, thatcorresponds to the estimated Doppler velocity, and a second phase shift,from one complex correlator output sample to a next complex correlatoroutput sample, that corresponds to the estimated Doppler velocity; andderotate an Nth complex sample pre or post correlator by a multiple ofone of the first phase shift and the second phase shift, depending onwhich phase shift was estimated.
 8. The radar sensing system of claim 1,wherein the control unit is operable to configure at least one receiverof the plurality of receivers to process the range information datastored in the memory, and wherein the at least one receiver isconfigured to: select an object for which better Doppler estimation isdesired; store multiple time scans corresponding to a range of a desiredobject; and perform Doppler processing on extended information frommultiple scans to obtain more precise Doppler information.
 9. The radarsensing system of claim 1, wherein the control unit is operable toconfigure at least one transmitter of the plurality of transmitters, andat least one receiver of the plurality of receivers to process the rangeinformation data stored in the memory; wherein the at least onetransmitter is configured to transmit with a first periodic code with agiven period N; wherein the at least one receiver is configured to storefirst N time correlator output samples; wherein the at least onetransmitter is configured to transmit with a second periodic code with asame period as the first periodic code; wherein the at least onereceiver is configured to store the second N time samples; wherein theat least one receiver is configured to perform Doppler processing oneach of K sets of N time samples to compute K frequency spectrums;wherein the at least one receiver is configured to compare a frequencyspectrum and identify frequencies where a Doppler magnitude is large inone spectrum but varies across the K frequency spectrums; wherein the atleast one receiver is configured to identify frequencies where theDoppler magnitude is large and remains substantially constant across theK frequency spectrums; wherein the at least one receiver is configuredto modify all captured time samples to remove Doppler processed samplescorresponding to frequencies that correspond to inconsistent signals;and wherein the at least one receiver is configured to perform a singleFFT over all K*N modified samples.
 10. The radar sensing system of claim1, wherein the control unit is operable to configure at least onereceiver of the plurality of receivers to process the range informationdata stored in the memory; wherein the at least one receiver isconfigured to perform spatial windowing and beamforming on one or moreinput complex sample vectors from Doppler information stored in a radardata cube 2 (RDC2) for a given range and Doppler for various receiversand/or virtual receivers to produce output complex sample vectors storedin a radar data cube 3 (RDC3) for the corresponding range and Dopplerand angle; wherein the at least one receiver is configured to identify aregion of samples in the RDC3 corresponding to a band of low absolutevelocity that includes known ground clutter; wherein the at least onereceiver is configured to store samples of the RDC3 in the identifiedband in a separate memory buffer called the static slice; wherein the atleast one receiver is configured to tag the samples in the identifiedband as being included in the static slice; wherein the at least onereceiver is configured to process the complete set of RDC3 samples byone of a processing the complete set of RDC3 samples by a decimator anda sparsifier; wherein the at least one receiver is configured to comparea magnitude of a sample to one or more thresholds configured by thecontrol unit for each untagged sample in the RDC3 and the decimator orthe sparsifier; wherein the at least one receiver is configured to storea set of samples that depends upon an outcome of the comparison; andwherein the at least one receiver is configured to include the sample inone or more distinct memory buffers.
 11. The radar sensing system ofclaim 10, wherein the set of samples stored includes all samples with asame range and Doppler.
 12. The radar sensing system of claim 10,wherein different thresholds are configured for different range bins.13. The radar sensing system of claim 10, wherein the thresholds aredetermined by analyzing histograms of RDC3 sample magnitudes.
 14. Theradar sensing system of claim 10, wherein the control unit is operableto configure at least one receiver of the plurality of receivers toprocess the range information data stored in the memory; wherein the atleast one receiver is configured to analyze a static slice and asparsified RDC3 (sRDC3) to identify regions of interest; wherein the atleast one receiver is configured to track regions of interest over time,including multiple scans, by storing relevant information in the memory;wherein the at least one receiver is configured to choose a subset ofthe range, Doppler, angle space based on past information and currentsamples of the static slice and/or the sRDC3 in the regions of interestin which to perform super resolution angle of arrival processing;wherein the at least one receiver is configured to select a subset ofthe range bins of a RDC1 on which to perform Doppler processing; whereinthe at least one receiver is configured to select a subset of theDoppler bins to perform super resolution processing; wherein the atleast one receiver is configured to configure a MUSIC (MUltiple SignalClassification) engine to provide super resolution processing on thesubset of range, Doppler, angle space; wherein the at least one receiveris configured to configure the MUSIC engine to determine location ofpeaks in the angular dimension for a specified subset of range, Doppler,angle space; wherein the MUSIC engine is configured to calculate asample covariance matrix from one or more samples of input data; whereinthe MUSIC engine is configured to perform spatial smoothing on thecovariance matrix; wherein the MUSIC engine is configured to calculate asingular value decomposition of the covariance matrix; wherein the MUSICengine is configured to use the singular values to estimate a number ofsignals; wherein the MUSIC engine is configured to use a sub-matrix ofthe left unitary matrix representing the noise subspace to compute theMUSIC spectrum over a specified range of angles; and wherein the MUSICengine is configured to write to an output FIFO a list of anglescorresponding to peaks of the MUSIC spectrum occurring in the specifiedrange of angles.
 15. The radar sensing system of claim 14, wherein theDoppler processing is performed by a channelizer.
 16. The radar sensingsystem of claim 14, wherein the configuration includes setting thenumber of spatial smoothing steps, and the parameters for singular valuedecomposition (SVD) calculation.
 17. The radar sensing system of claim14, wherein the control unit configures the MUSIC engine by providingcommands and parameters through a FIFO.
 18. The radar sensing system ofclaim 1, wherein the control unit further configures each transmitter ofthe plurality of transmitters and each receiver of the plurality ofreceivers to correlate with a specified set of range bins to generatethe range information data stored in memory.
 19. The radar sensingsystem of claim 18, wherein a difference between consecutive range binsincreases as the range increases.
 20. The radar sensing system of claim1 wherein a modification of the processing of the range information datais dependent on external information received by the radar system.
 21. Amethod for operating a dynamically adaptable, modulated continuous wavevehicular radar system, the method comprising: providing a transmitterconfigured for installation and use on a vehicle; providing a receiverconfigured for installation and use on the vehicle; providing a memory;wherein the receiver comprises a dynamically adaptable digital front endprocessor and a dynamically adaptable digital back end processor;transmitting a radio signal using the transmitter; receiving a radiosignal using the receiver, wherein the received radio signal is atransmitted radio signal reflected from an object in the environment;wherein, in response to environmental conditions and an operationalstatus, selecting an operating mode with respect to currentenvironmental conditions and a current operational status, and modifyingan operational parameter of at least one of the transmitter and thereceiver depending on a need for one of a best range resolution and abest velocity resolution; storing range information data into the memorythat was produced by the digital front end processing unit; anddirecting the digital back end processor to process a selected portionof the range information data based upon the selected operating mode.22. A radar sensing system for a vehicle, the radar sensing systemcomprising: a transmitter configured for installation and use on avehicle, wherein the transmitter is configured to transmit a radiosignal; a receiver configured for installation and use on the vehicle,wherein the receiver is configured to receive a radio signal, andwherein the received radio signal is a transmitted radio signalreflected from an object in the environment; a memory; a control unitconfigured to select an operating mode and to modify an operationalparameter of at least one of the transmitter and the receiver, whereinan operating mode is selected based on current environmental conditionsand a current operational status, and wherein the operational parameteris modified based on one of a best range resolution and a best velocityresolution; wherein range information data produced by the receiver isstored in the memory and then subjected to further processing, asdirected by the control unit, based upon the selected operating mode.